Hot air engines have been around for approximately two hundred years in many successful designs. Hot air engines derive their power from the expansion and contraction of a gas, usually air that is heated and cooled to ultimately drive a crank. Many hot air engines work in a thermodynamic process knows as a Stirling cycle, named after Robert Stirling, a 19th century inventor.
All heat engines take a certain amount of heat and convert a percentage into work, while rejecting the remaining energy at a lower temperature. Schematically, as heat moves through the engine, from the hot to the cold side, the engine converts some of that energy into work. The key is that only a portion of that heat can be converted into work. The rest has to be expelled to a cold reservoir. The maximum efficiency can be mathematically calculated and is dependent upon the difference between the hot and cold reservoir. The greater the disparity, the more efficient the engine can be.
A heat pump is essentially a heat engine operating in reverse. Schematically, it resembles a heat engine with the directional arrows reversed. Energy is added and cold moves through the heat pump towards the hot side. Work must be added because hot naturally wants to move toward cold, so to make it go the other way, requires the addition of energy.
While in reality one can only achieve a fraction of the maximum efficiency, it is important to understand the heat engine process correctly as all engines from lawn mower engines to rocket engines utilize it. One cannot actually determine the thermal efficiency of an engine without an understanding of these basic thermodynamic principles. Challenges arise in that no engine or heat pump made looks and works like the ideal schematic representation. The present invention features a hot air engine system that looks and works like the ideal schematic representation. The present invention is a small solar and alternative fuel engine that will sit on a desk top and will run both clockwise and counterclockwise depending on which side of the engine is hot or cold. It will run when powered by solar energy with a Fresnel lens, or with a candle, or small alcohol burner. It will generate enough electricity to run a small motor or charge a battery while turning a five bladed seven inch fan. The engine will also work as a reversible heat pump when turned by an outside power source such as a drill.
Any feature or combination of features described herein are included within the scope of the present invention provided that the features included in any such combination are not mutually inconsistent as will be apparent from the context, this specification, and the knowledge of one of ordinary skill in the art. Additional advantages and aspects of the present invention are apparent in the following detailed description and claims.